My app uses multiple databases. I'd like to authenticate with a user stored in the admin db that has readWriteAnyDatabase permissions.

Currently, my mongoid.yml looks something like this:

production:
  sessions:
    default:
      hosts:
        - my.mongo.com:27017
      database: default_db
      username: admin_user
      password: admin_pw

The problem is that Mongoid will authenticate with admin_user@default_db instead of admin_user@admin. So authentication always ends up failing

I'd like to keep default_db as my default database, but I'd also like to authenticate with admin_user@admin. Is there a good way to accomplish this?

(Here's someone else dealing with the same issue)